1. Field of the Invention
The field of this invention comprises catalysts for the polymerization of olefins, particularly ethylene. The preferred commercial catalysts used heretofore have been combinations of alkyl- and aryl-substituted aluminum compounds with a variety of metal compounds.
2. Description of the Prior Art
The prior art which appears most pertinent to the subject invention includes U.S. Pat. Nos. 3,113,115; 3,114,743; 3,257,332; and 3,574,138, which disclose two-component polymerization catalyst systems and U.S. Pat. No. 3,349,064 which discloses a three-component system. Of particular interest is U.S. Pat. No. 3,257,332, which discloses a two-component catalyst system comprising (A) an aluminum trialkyl and (B) a compound of a metal on the left-hand side of the IV to VI Groups of the Periodic System with the preferred compounds including salts of chromium where "salts" are not specifically defined but apparently include halides, acetylacetonates and butylates. Also of particular interest is U.S. Pat. No. 3,349,064, which discloses a three-component catalyst system comprising (A) an aluminum trialkyl, (B) a solvent-soluble vanadium compound and (C) a promoter defined as "unsaturated carbocyclic compounds containing at least 4 halogen atoms, at least 2 of which are attached to doubly bonded carbon atoms and at least one of which is attached to a single bound carbon atom alpha to the double bond." The disclosures of these references are hereby incorporated by reference.